It’s amazing that young people can even get auto insurance in the cinematic world of teen comedies. From "Sixteen Candles" to "Ferris Bueller’s Day Off," the mortality rate of a parent or sibling’s prized car has to be about 85 percent.

There are no safe driving bonuses in "Fun Size," a film that covers the high school party comedy checklist well, but doesn’t make its own mark on the genre. Well-written but weakly executed, it’s hard to imagine anyone is going to cherish this film, if they even remember it in three months time.

"Fun Size" is the directorial debut of Josh Schwartz, who developed the teen television dramas "The O.C." and "Gossip Girl." He didn’t write the script, but the film reflects his ability to capture young people authentically, while simultaneously translating for older generations. His fingerprints are all over the narrative. Example: In the Schwartz universe, all so-called nerds are exactly one accessory (usually a pair of dorky glasses or a jacket) from looking like a model.

He also executes the John Hughes trick of making parents seem alien but still likable. In about four minutes of screen time, Ana Gasteyer as a lesbian mom reaffirms that she’s among the most underrated "Saturday Night Live" cast members of all time.

The focus in "Fun Size" is on teen science whiz Wren (Victoria Justice), who has captured the attention of her high school’s Alpha male. Fellow geek Roosevelt (Thomas Mann) completes the love triangle. On the way to the big party, Wren’s prank-loving 8-year-old brother gets lost trick-or-treating. The last two-thirds of the movie is a combination of "Problem Child" and "The Fugitive," if both were reimagined as a 1980s Molly Ringwald vehicle.

The story lacks momentum, with a particularly useless subplot involving a convenience-store clerk. He’s one of several disturbing adults who choose to recruit the second-grader as a criminal accomplice or mascot — ignoring all child safety seat laws — instead of notifying police about his whereabouts.

That would be easier to stomach in a movie with more focus, but "Fun Size" seems trapped in a limbo between a hyperkinetic comedy for kids and something more outlaw for teens. PG-13 may have been the lucrative move, but it feels like there’s an internal struggle going on between PG and R.

Screenwriter Max Werner, a veteran of "The Colbert Report," shows he can write a good script under any circumstance. Individual moments shine, such as Wren’s hero worship for Ruth Bader Ginsburg, and a witty scene where Wren’s mom (Chelsea Handler) bonds with the parents of her too-young boyfriend’s best friend.

And then there’s the destruction of Roosevelt’s Volvo, borrowed from his mother, which is violated in a particularly entertaining way. On the teen comedy scale, it falls somewhere between the fate of Joel Goodson’s dad’s Porsche in "Risky Business" and Charles Jefferson’s car in "Fast Times at Ridgemont High." Hope someone’s old man has an ultimate set of tools …